<!DOCTYPE html>
<meta charset="utf-8">
<meta property="og:image" itemprop="image primaryImageOfPage" content="https://hajimehoshi.github.io/ebiten/images/examples/sprites.png">
<meta name="description" content="Ebiten example - sprites">
<link rel="shortcut icon" href="../favicon.png" type="image/png" >
<link rel="icon" href="../favicon.png" type="image/png" >
<title>Ebiten example - sprites</title>

<link rel="stylesheet" href="../stylesheets/bootstrap.min.css">
<link rel="stylesheet" href="../stylesheets/highlight-github.css">
<link rel="stylesheet" href="../stylesheets/ebiten.css">
<script src="../scripts/googleanalytics.js"></script>

<nav class="navbar"><div class="container">
  <nav class="d-flex flex-row" style="width: 100%;">
    <div class="nav mr-auto"><a class="navbar-brand" href="../"><img src="../images/logo_white.svg" alt="EBITEN"></a></div>
    <ul class="nav">
      <li class="nav-item"><a class="nav-link" href="https://github.com/hajimehoshi/ebiten">GitHub</a></li>
      <li class="nav-item"><a class="nav-link" href="https://godoc.org/github.com/hajimehoshi/ebiten">GoDoc</a></li>
      <li class="nav-item"><a class="nav-link" href="https://github.com/hajimehoshi/ebiten/wiki">Wiki</a>
      <li class="nav-item"><a class="nav-link" href="https://ebiten-playground.github.io/">Playground</a>
    </ul>
  </nav>
</div></nav>

<main><div class="container">

  <h2>Ebiten example - sprites</h2>
  <iframe src="sprites.content.html" width="640" height="480"></iframe>
  <div class="card"><pre class="card-body"><code class="language-go">// &#43;build example

package main

import (
        &#34;fmt&#34;
        _ &#34;image/png&#34;
        &#34;log&#34;
        &#34;math&#34;
        &#34;math/rand&#34;

        &#34;github.com/hajimehoshi/ebiten&#34;
        &#34;github.com/hajimehoshi/ebiten/ebitenutil&#34;
)

const (
        screenWidth  = 320
        screenHeight = 240
        maxAngle     = 256
)

var (
        ebitenImage *ebiten.Image
)

type Sprite struct {
        imageWidth  int
        imageHeight int
        x           int
        y           int
        vx          int
        vy          int
        angle       int
}

func (s *Sprite) Update() {
        s.x &#43;= s.vx
        s.y &#43;= s.vy
        if s.x &lt; 0 {
                s.x = -s.x
                s.vx = -s.vx
        } else if screenWidth &lt;= s.x&#43;s.imageWidth {
                s.x = 2*(screenWidth-s.imageWidth) - s.x
                s.vx = -s.vx
        }
        if s.y &lt; 0 {
                s.y = -s.y
                s.vy = -s.vy
        } else if screenHeight &lt;= s.y&#43;s.imageHeight {
                s.y = 2*(screenHeight-s.imageHeight) - s.y
                s.vy = -s.vy
        }
        s.angle&#43;&#43;
        s.angle %= maxAngle
}

type Sprites struct {
        sprites []*Sprite
        num     int
}

func (s *Sprites) Update() {
        for _, sprite := range s.sprites {
                sprite.Update()
        }
}

const (
        MinSprites = 0
        MaxSprites = 50000
)

var (
        sprites = &amp;Sprites{make([]*Sprite, MaxSprites), 500}
        op      = &amp;ebiten.DrawImageOptions{}
)

func init() {
        img, _, err := ebitenutil.NewImageFromFile(&#34;_resources/images/ebiten.png&#34;, ebiten.FilterDefault)
        if err != nil {
                log.Fatal(err)
        }
        w, h := img.Size()
        ebitenImage, _ = ebiten.NewImage(w, h, ebiten.FilterDefault)
        op := &amp;ebiten.DrawImageOptions{}
        op.ColorM.Scale(1, 1, 1, 0.5)
        ebitenImage.DrawImage(img, op)
        for i := range sprites.sprites {
                w, h := ebitenImage.Size()
                x, y := rand.Intn(screenWidth-w), rand.Intn(screenHeight-h)
                vx, vy := 2*rand.Intn(2)-1, 2*rand.Intn(2)-1
                a := rand.Intn(maxAngle)
                sprites.sprites[i] = &amp;Sprite{
                        imageWidth:  w,
                        imageHeight: h,
                        x:           x,
                        y:           y,
                        vx:          vx,
                        vy:          vy,
                        angle:       a,
                }
        }
}

func update(screen *ebiten.Image) error {
        // Decrease the nubmer of the sprites.
        if ebiten.IsKeyPressed(ebiten.KeyLeft) {
                sprites.num -= 20
                if sprites.num &lt; MinSprites {
                        sprites.num = MinSprites
                }
        }

        // Increase the nubmer of the sprites.
        if ebiten.IsKeyPressed(ebiten.KeyRight) {
                sprites.num &#43;= 20
                if MaxSprites &lt; sprites.num {
                        sprites.num = MaxSprites
                }
        }

        sprites.Update()

        if ebiten.IsRunningSlowly() {
                return nil
        }

        // Draw each sprite.
        // DrawImage can be called many many times, but in the implementation,
        // the actual draw call to GPU is very few since these calls satisfy
        // some conditions e.g. all the rendering sources and targets are same.
        // For more detail, see:
        // https://godoc.org/github.com/hajimehoshi/ebiten#Image.DrawImage
        w, h := ebitenImage.Size()
        for i := 0; i &lt; sprites.num; i&#43;&#43; {
                s := sprites.sprites[i]
                op.GeoM.Reset()
                op.GeoM.Translate(-float64(w)/2, -float64(h)/2)
                op.GeoM.Rotate(2 * math.Pi * float64(s.angle) / maxAngle)
                op.GeoM.Translate(float64(w)/2, float64(h)/2)
                op.GeoM.Translate(float64(s.x), float64(s.y))
                screen.DrawImage(ebitenImage, op)
        }
        msg := fmt.Sprintf(`FPS: %0.2f
Num of sprites: %d
Press &lt;- or -&gt; to change the number of sprites`, ebiten.CurrentFPS(), sprites.num)
        ebitenutil.DebugPrint(screen, msg)
        return nil
}

func main() {
        if err := ebiten.Run(update, screenWidth, screenHeight, 2, &#34;Sprites (Ebiten Demo)&#34;); err != nil {
                log.Fatal(err)
        }
}
</code></pre></div>

</div></main>

<footer><div class="container">
  <p>© 2013 Hajime Hoshi</p>
  <p>Code is licensed under <a href="https://github.com/hajimehoshi/ebiten/blob/master/LICENSE">the Apache License 2.0</a>.</p>
  <p>The content of this page is licensed under <a href="https://creativecommons.org/licenses/by/4.0/">the Creative Commons Attribution 4.0 License</a>.</p>
</div></footer>

<script src="../scripts/highlight.pack.js"></script>
<script>hljs.initHighlightingOnLoad();</script>
